package com.wxg.ch12;

import com.wxg.util.Res;

import java.util.ArrayList;

public class AVLTree<K extends Comparable<K>, V> {

    private class Node {
        public K key;
        public V value;
        public Node left, right;

        public int height;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }
    }

    private Node root;
    private int size;

    public AVLTree() {
        root = null;
        size = 0;
    }

    public int getSize() {
        return size;
    }

    private int getHeight(Node node) {
        if (node == null) {
            return 0;
        }
        return node.height;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * 判断该二叉树是否是一棵二分搜索树
     * @return
     */
    public boolean isBST() {
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root, keys);
        for (int i = 1; i < keys.size(); i++) {
            if (keys.get(i-1).compareTo(keys.get(i)) > 0) {
                return false;
            }
        }
        return true;
    }

    private void inOrder(Node node, ArrayList<K> keys) {
        if (node == null) {
            return;
        }

        inOrder(node.left, keys);
        keys.add(node.key);
        inOrder(node.right, keys);
    }

    /**
     * 判断该二叉树是否是一个平衡二叉树
     * @return
     */
    public boolean isBalanced() {
        return isBalanced(root);
    }

    private boolean isBalanced(Node node) {
        if (node == null) {
            return true;
        }

        int blanceFactor = getBalanceFactor(node);
        if (Math.abs(blanceFactor) > 1) {
            return false;
        }

        return isBalanced(node.left) && isBalanced(node.right);
    }

    /**
     * 获得节点 node 的平衡因子
     *
     * @param node
     * @return
     */
    private int getBalanceFactor(Node node) {
        if (node == null) {
            return 0;
        }
        return getHeight(node.left) - getHeight(node.right);
    }


    /**
     *
     *  // 对节点y进行向右旋转操作，返回旋转后新的根节点x
     *  //        y                              x
     *  //       / \                           /   \
     *  //      x   T4     向右旋转 (y)        z     y
     *  //     / \       - - - - - - - ->    / \   / \
     *  //    z   T3                       T1  T2 T3 T4
     *  //   / \
     *  // T1   T2
     *
     * @param y
     * @return
     */
    private Node rightRotate(Node y) {
        Node x = y.left;
        Node T3 = x.right;

        // 向右旋转的过程
        x.right = y;
        y.left = T3;

        // 更新 height
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

        return x;
    }

    /**
     *
     * // 对节点y进行向左旋转操作，返回旋转后新的根节点x
     * //    y                             x
     * //  /  \                          /   \
     * // T1   x      向左旋转 (y)       y     z
     * //     / \   - - - - - - - ->   / \   / \
     * //   T2  z                     T1 T2 T3 T4
     * //      / \
     * //     T3 T4
     *
     * @param y
     * @return
     */
    private Node leftRotate(Node y) {
        Node x = y.right;
        Node T2 = x.left;

        // 向左旋转过程
        x.left = y;
        y.right = T2;

        // 更新 height
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

        return x;
    }

    public void add(K key, V value) {
        root = add(root, key, value);
    }

    private Node add(Node node, K key, V value) {
        if (node == null) {
            size ++;
            return new Node(key, value);
        }

        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else {
            node.value = value;
        }

        // 更新 height
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(node);

        // 平衡维护
        // LL
        if (balanceFactor > 1 && getBalanceFactor(node.left) >= 0) {
            return rightRotate(node);
        }

        // RR
        if (balanceFactor < -1 && getBalanceFactor(node.right) <= 0) {
            return leftRotate(node);
        }

        // LR
        if (balanceFactor > 1 && getBalanceFactor(node.left) < 0) {
            node.left = leftRotate(node.left);
            return rightRotate(node);
        }

        // RL
        if (balanceFactor < -1 && getBalanceFactor(node.right) > 0) {
            node.right = rightRotate(node.right);
            return leftRotate(node);
        }
        return node;
    }

    /**
     * 返回以 node 为根节点的二分搜索树中，key 所在的节点
     *
     * @param node
     * @param key
     * @return
     */
    private Node getNode(Node node, K key) {
        if (node == null) {
            return null;
        }

        if (key.equals(node.key)) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else {
            return getNode(node.right, key);
        }
    }

    public boolean contains(K key) {
        return getNode(root, key) != null;
    }

    public V get(K key) {
        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (node == null) {
            throw new RuntimeException(key + " doesn't exist!");
        }

        node.value = newValue;
    }

    private Node minimum(Node node) {
        if (node.left == null) {
            return node;
        }

        return minimum(node.left);
    }

    public V remove(K key) {
        Node node = getNode(root, key);
        if (node != null) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key) {
        if (node == null) {
            return null;
        }

        Node retNode;
        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            retNode = node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            retNode = node;
        } else {
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                retNode = rightNode;
            }else if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size --;
                retNode = leftNode;
            } else {
                Node successor = minimum(node.right);
                successor.right = remove(node.right, successor.key);
                successor.left = node.left;

                node.left = node.right = null;
                retNode = successor;
            }
        }

        if (retNode == null) {
            return null;
        }

        // 更新 height
        retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(retNode);

        // 平衡维护
        // LL
        if (balanceFactor > 1 && getBalanceFactor(retNode.left) >= 0) {
            return rightRotate(retNode);
        }

        // RR
        if (balanceFactor < -1 && getBalanceFactor(retNode.right) <= 0) {
            return leftRotate(retNode);
        }

        // LR
        if (balanceFactor > 1 && getBalanceFactor(retNode.left) < 0) {
            retNode.left = leftRotate(retNode.left);
            return rightRotate(retNode);
        }

        // RL
        if (balanceFactor < -1 && getBalanceFactor(retNode.right) > 0) {
            retNode.right = rightRotate(retNode.right);
            return leftRotate(retNode);
        }
        return retNode;
    }

    public static void main(String[] args) {
        System.out.println("Pride and Prejudice");

        ArrayList<String> words = new ArrayList<>();
        String filename = Res.root("pride-and-prejudice.txt");
        if (FileOperation.readFile(filename, words)) {
            System.out.println("Total words: " + words.size());

            AVLTree<String, Integer> map = new AVLTree<>();
            for (String word : words) {
                if (map.contains(word)) {
                    map.set(word, map.get(word) + 1);
                } else {
                    map.add(word, 1);
                }
            }
            System.out.println("Total different words: " + map.getSize());
            System.out.println("Frequency of PRIDE: " + map.get("pride"));
            System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));

            System.out.println("is BST : " + map.isBST());
            System.out.println("is Balanced : " + map.isBalanced());

            for (String word : words) {
                map.remove(word);
                if (!map.isBalanced() || !map.isBST()) {
                    throw new RuntimeException("Error!");
                }
            }
            System.out.println("完成!");
        }
        System.out.println();

    }
}
